A study of estrogen in the growth and cytodifferentiation of the anterior pituitary is proposed. Pituitaries from prenatal, neonatal and adult animals will be studied. Dry mount autoradiography will be used to determine if fetal or neonatal pituitaries will bind H3-estradiol. Neonatal animals will be surgically and hormonally treated and their pituitaries examined for ultrastructural changes. Organ cultures of prenatal and neonatal pituitaries will be treated with estradiol and releasing hormones and examined by electron microscopy. The effects of estrogen on the DNA, RNA and protein synthesis of neonatal pituitaries will be studied with autoradiography and liquid scintillation techniques. Uptake of labeled precursors will be examined in vivo and in vitro. Experimental treatment of neonatal animals will determine if estradiol is involved in these parameters. Cell cultures will show any direct effect. Binding studies will be undertaken to determine if sexual differences are present and which factors are involved. Because of the widespread use of oral contraceptives, a more thorough understanding of the effect of estrogen on pituitary cells is needed. This investigation has relevancy to the fields of studies involving birth defects and tumor formation.